Before using conventional drinking cups, most infants and children drink from vessels designed specifically for their use, for example, nursers and spill proof cups. To facilitate grasping many of these nursers and spill proof cups have at least one, and more often two handles, permanently affixed to opposite sides of the vessel. When the child holds a handled vessel, her hands are positioned 180° apart. This 180° orientation always causes the hands to be placed at the furthest possible distance between them. Having the hands in this orientation is not always the most comfortable or optimal position for the child. Sometimes it is desirable to have the hands oriented at a different angle, for example, 90°. Having the hands closer together may help facilitate the holding of the vessel.
Although some prior art drinking vessels have adjustable handles, such prior art drinking vessels do not allow the handles to remain fixed once they have been adjusted to a desired setting. For example, the handles of such prior art drinking vessels will undesirably change position when the vessel is dropped onto the floor. Other prior art drinking vessels with locking handles only allow the handles to be readjusted if the entire drinking vessel were disassembled. Thus, there is a need for drinking vessels with adjustable handles that remain locked after the handles have been properly oriented and that can be easily readjusted, if needed, without resorting to disassembling the entire drinking vessel.